The hypothesis that this study attempts to test is that a new experimental approach to the education and treatment of preschool autistic children will be more effective (both initially and at follow-up) than techniques which represent the best of current practice. The specific aims include: a) replication of treatment effects across a heretofore underrepresented subset of autistic children; b) continued follow-up of former clients; and, c) assessment of self-management strategies to improve the long-term adjustment of clients. The key feature of the intervention model is the use of normal peers both as role models for autistic children, and as direct instructional agents in a developmentally integrated setting. The experimental program also makes use of other aspects of treatment which are believed to be advances on existing practice. Specifically, there is a heavy emphasis on curriculum content established by observation of comparable but successfully adjusted children, the use of various procedures to encourage parents to participate as teachers and therapists for their children, and group-based instruction of autistic and typical children. Another important feature of the experimental program is the use of continuous behavioral observation and feedback on intervention effectiveness such that efficacious interventions can readily be established on a child-by-child basis. Based on our first six years of data we expect such peer-mediated interventions to be more effective than conventional, adult-mediated treatments of autistic children, that occur in developmentally segregated environments (i.e., groups restricted to problem children). It is anticipated that peer involvement in the experimental program will continue to have only positive effects on nonhandicapped children's developmental, class deportment, and social skills. Finally, it is expected that the majority of experimentally-treated autistic children will continue to function successfully as they progress through regular elementary and secondary school classes.